A microphone array device which employs a plurality of microphones as sound collection devices in a sound field is known. A technology which targets sound signals which are to be collected in targeted positions from among sound signals which are collected from microphones which are actually arranged instead of actually installing microphones and collecting sound in that manner has been proposed with the object of reducing the number of microphones in the microphone array device. The invention of Patent Document 1 is representative of this technology and estimates the sound collection signals in arbitrary positions in dimensional directions in the number of two microphones for each dimension.
According to the invention of Patent Document 1, as shown in FIG. 6, two microphones 10a and 10b are arranged in an axial direction and sound signals which are collected thereby are input to a received sound signal estimation processing unit 11. The received sound signal estimation processing unit 11 approximates the sound waves which arrive at the two microphones from the sound source to planar waves, renders an approximation of the estimated received sound signals in a position which is coaxial with the microphones 10a and 10b by means of a wave equation, estimates the coefficient b cos θ of the wave equation which is dependent on the direction of arrival of the sound waves of the wave equation by estimating the average power of the sound waves arriving at the two microphones to be equal, and estimates the received sound signals from the two microphones in an arbitrary position which is coaxial with the microphones on the basis of the received sound signals.    Patent Document 1: Japanese Unexamined Patent Publication No. 2001-45590
Furthermore, the invention of Patent Document 1 performs signal processing which approximates the signals arriving at the two microphones from the sound source as planar waves. However, the sound waves in the actual sound field are not limited to being planar waves, meaning that the estimated positions of the received sound signals cannot be accurately obtained.
In addition, although detecting the phase difference, time difference, and frequency difference of the sounds collected by a plurality of microphones and estimating the received sound signals in an arbitrary position based on these differences may also be considered, in this case, when the plurality of microphones are arranged in proximity to one another, the detected value for the phase difference or the like is diminished and erroneous effects are readily introduced, making an accurate estimate difficult.
Furthermore, generally speaking, in the field of sound collection or the editing field, the setting of the sound amount is in a suitable state and the setting conditions for the sound collection and editing cannot be improved and must always be confirmed. For example, in cases where sound collection for a 5.1-channel surround system is carried out, a 5.1-channel reproduction system must actually be prepared and monitored. However, it is difficult to prepare a bulky reproduction system of this kind in the sound collection field and monitoring has generally been performed using headphones or two-channel monitor speakers. However, it has hitherto not been possible to confirm the status (the magnitude of the sound and the quality of each image fixed position) of each channel (the sound in each direction) of multichannel collected sound using conventional two-channel headphones or speakers.